DE 102 57 749 B4 discloses an inspection machine that inspects containers, which are filled with a product and closed, for contaminants, e.g. glass fragments. To this end, the container is first caused to rotate about its own axis until the product, the liquid, (partially) follows the rotation. Subsequently, the container is stopped while the liquid continues to rotate. In this condition, the container is illuminated and observed by means of a camera. In this so-called spin-stop process, the motion of the liquid cannot be seen in the camera image, whereas the contaminant and its motion are visible.
Contaminants may be the following ones: glass fragments or other solid matter that are not desired in the product, in particular glass fragments are dangerous to the consumer.
WO9714956A1 discloses that, depending on the CO2 content and the degree of dissolution of the CO2 in the product, fine gas bubbles may form in CO2-containing products, such as beer, cola, lemonade and others, during rotation about the bottle's own axis. These gas bubbles as well as possible foreign bodies move in the product and in a bottle, respectively. Differentiating gas bubbles and foreign bodies according to the above-mentioned spin-stop method is hardly possible in such cases.
The possibility that bottles may be discharged/sorted out by mistake due to gas bubbles instead of foreign bodies is given. This could be minimized through a long dwell time between filling and inspection, but this necessitates long transport distances or very large bulk conveyors. Such technical retrofitting is, moreover, complicated and leads to an increase in production costs.
The formation of undesired gas bubbles in CO2-containing products may be caused not only by the inspection process itself but also by various other disturbances in a CO2-containing product in the course of its production cycle.